Fingerprint verification apparatus, fingerprint verification method and a fingerprint verification program

ABSTRACT

An overlapped portion of a plurality of partial images of a fingerprint that are input from a fingerprint input device ( 7 ) is corrected to be reconfigured at a reconfiguration process section ( 106 ). The characteristics are extracted from the input partial images at the fingerprint characteristic information extracting section ( 110 ) and the extracted characteristic information is stored in an input characteristic information memory. A verification process section executes DP comparison (dynamic programming method) between the characteristic information stored in the input characteristic information memory and the characteristic information stored in the registered characteristic information memory. The distance value obtained by the DP comparison is compared to a threshold that is previously set. If the distance value is smaller than the threshold, it is judged the fingerprint is identified and if the distance value is larger than the threshold, it is judged that the fingerprint is not identified.

TECHNICAL FIELD

The present invention relates to a fingerprint verification apparatusand a fingerprint verification method and a program for verifying afingerprint by a computer for identifying a person.

BACKGROUND OF THE INVENTION

Recently, interests have been focused on the security technology forcontrolling access to information as the rapid progress is made in theelectronic information and the network information. As one of thesecurity technology, various products for identifying a person byfingerprint verification have been proposed.

For identifying a person, after a fingerprint image is firstly input bya fingerprint sensor, the input fingerprint image is necessary to beverified with registered fingerprint images. As fingerprint verificationmethods, the characteristic extracting verification method (Minutia(e)matching) and the image matching method (pattern matching method) areconventionally known.

In the characteristic extracting verification method, the structure ofthe terminations or the bifurcations of the raised portion (ridge) ofthe fingerprint is extracted as the characteristics (minutia) and thecharacteristics are compared to verify the fingerprint. Thecharacteristics are extracted after the noise is removed from the inputfingerprint image and the image processing such as the contrastprocessing or the processing of making fine lines is executed. In thismethod, various rules are included in the program so as not to extractthe false characteristics according to the condition of fingers wheninputted and the image processing. Therefore, the program includes acomplicated algorism and the verification processing time may be varied.

In the image matching method, the similarity of the fingerprint image isdirectly compared. Because the similarity is checked by shifting theregistered fingerprint image and the input fingerprint image, theverification process can be executed relatively fast. However, since thefingerprint image is input and stored, the fingerprint image may beelectrically copied. Therefore, it is necessary to settle the securityproblems.

However, in those conventional methods, either the characteristics areextracted with respect to an image of a whole fingerprint or the wholeimage is used for verification, so it is required to have a large amountof memory for storing the whole image and a large amount of computing.Therefore, there have been problems in reducing the size of theapparatus and reducing the cost.

To solve the above problems, an object of the present invention is toprovide a fingerprint verification apparatus, a fingerprint verificationmethod and a fingerprint verification program for being capable ofverifying a fingerprint by extracting a characteristic information froma partial image of a fingerprint without storing a whole image of thefingerprint.

DISCLOSURE OF THE INVENTION

A fingerprint verification apparatus of this invention for verifying afingerprint based on an input image of a fingerprint comprisescharacteristic information extracting means for computing and extractinga characteristic information from a partial image of a fingerprint andidentifying means for identifying the fingerprint on the basis of thecharacteristic information extracted by the characteristic informationextracting means.

According to the above-structured fingerprint verification apparatus,since the characteristic information is extracted from the partial imagefor identifying the fingerprint, it is not necessary to store a wholeimage of the fingerprint. Therefore, a large amount of memory forstoring the image of whole fingerprint is not necessary. Further, theimage of whole fingerprint may not be electronically copied. Since thepartial image is defined in small, the calculation amount for obtainingthe characteristic information can be reduced. If the characteristicinformation extracting process is executed separately from theidentifying process, the processes can be executed simultaneously andthe whole processes can be executed fast.

In addition to the above structure, the fingerprint verificationapparatus of the present invention may have fingerprint input means forinputting a partial image of the fingerprint, and image process meansfor comparing a plurality of partial images of fingerprints inputted bythe fingerprint input means and removing an overlapped portion. Thecharacteristic information extracting means may extract thecharacteristic information from the partial image of the fingerprintwhere the overlapped portion is removed by the image process means.

In the fingerprint verification apparatus, a plurality of partial imagesthat are input one after another are combined and the overlappedportions are removed to be reconfigured. Therefore, it can be preventedthat the characteristic information is extracted repeatedly from theoverlapped portion. Load for extracting the characteristic informationcan be reduced.

The fingerprint verification apparatus of the present invention may havestoring means for storing a characteristic information of at least oneand the identifying means may compare and verify the at least onecharacteristic information stored by the storing means with at least onecharacteristic information that is extracted by the characteristicinformation extracting means to identify the fingerprint.

In the fingerprint verification apparatus, since the fingerprint can beidentified by comparing and verifying the stored characteristicinformation of a partial image with the characteristic information of aninput partial image, it is not necessary to store the characteristicinformation of the whole fingerprint in the storing means and a volumeof the storing means can be reduced.

In the fingerprint verification apparatus of the present invention, thecharacteristic information extracting means may execute a frequencyanalysis computing process to extract frequency spectrum information ofthe partial image of the fingerprint as the characteristic information.

In the above structured fingerprint verification apparatus, thecharacteristics (minutia) are not extracted from the fingerprint.Information of the ridge is processed by the frequency analysiscomputing process to obtain the characteristic information. Therefore, apreprocessing time of the image can become short and the process can beexecuted fast. Moreover, there is no difference in difficulty ofextracting of the characteristics caused by a condition of a finger whenan image is inputted. Therefore, the process time can be stable.

In the fingerprint verification apparatus of the present invention, thecharacteristic information extracting means may use one of a linearpredictive coding (LPC) computing process, a group delay spectrum (GDS)computing process and a fast Fourier transform (FFT) computing processas the frequency analysis computing process.

In the above structured fingerprint verification apparatus, acharacteristic information can be extracted easily and fast to executethe fingerprint verification process by using the known frequencyanalysis computing process such as voice analysis for extracting acharacteristic information.

In the fingerprint verification apparatus of the present invention, thefingerprint input means may input a line image of more than or equal toone image line as a partial image of a fingerprint and the image processmeans may detect an overlapped image line from the two partial images ofa fingerprint that are continuously input by the fingerprint input meansand may remove the overlapped image line from one of the partial imagesof the fingerprint.

In the above structured fingerprint verification apparatus, since theimage process means processes and reconfigures every two input partialimages, the memory amount for storing the input partial images can beminimum. Further, since the input operation and the image process can beexecuted at the same time, the operation can be executed fast.

The fingerprint verification apparatus of the present invention, theimage process means may execute an image reduction process in at leastone of a raster direction and a line direction of the partial image ofthe fingerprint where the overlapped portion is removed.

In the above structured fingerprint verification apparatus, for examplewhen the image reduction process is executed in a raster direction incase that the LPC calculation process is used for extracting thecharacteristic information, the dimension necessary for the calculationis decreased. Therefore, the memory amount for storing thecharacteristic information can be decreased. When the image reductionprocess is executed in a line direction, the number of times forcalculating the characteristic information is decreased. Therefore, thememory amount for storing the characteristic information can bedecreased.

The fingerprint verification apparatus of the present invention, theidentifying means may use the DP method (dynamic programming method).

In the above structured fingerprint verification apparatus, even if thedetection accuracy of the movement amount is low and the whole length ofthe fingerprint is different between the characteristic information ofthe registration time and the verification time, the difference betweenthe length of the fingerprints that are to be verified is absorbed andthe verification of the fingerprints can be executed.

A fingerprint verification method of the present invention for verifyinga fingerprint based on an input image of a fingerprint comprises acharacteristic information extracting step of computing and extracting acharacteristic information from a partial image of a fingerprint and anidentifying step of identifying the fingerprint on the basis of thecharacteristic information extracted at the characteristic informationextracting step.

In the above structured fingerprint verification method, since thecharacteristic information that is extracted from the partial image isused for identifying the fingerprint, it is not necessary to store awhole image of the fingerprint. Therefore, a large amount of memory forstoring the image of whole fingerprint is not necessary. Further, theimage of whole fingerprint may not be electronically copied. Since thepartial image is defined in small, the calculation amount for obtainingthe characteristic information can be reduced. If the characteristicinformation extracting process is executed separately from theidentifying process, the processes can be executed simultaneously andthe whole processes can be executed fast.

The fingerprint verification method of the present invention may have afingerprint inputting step of inputting a partial image of thefingerprint and image processing step of comparing a plurality ofpartial images of fingerprints inputted at the fingerprint inputtingstep and removing an overlapped portion. At the characteristicinformation extracting step the characteristic information may beextracted from the partial image of the fingerprint where the overlappedportion is removed at the image processing step.

In the above structured fingerprint verification method, a plurality ofpartial images that are input one after another are combined and theoverlapped portions are removed to be reconfigured. Therefore, it can beprevented that the characteristic information is extracted repeatedlyfrom the overlapped portion. Load for extracting the characteristicinformation can be reduced.

The fingerprint verification method of the present invention may have astoring step of storing a characteristic information of at least one,and at the identifying step the at least one characteristic informationstored at the storing step may be compared and verified with at leastone characteristic information that is extracted at the characteristicinformation extracting step to identify the fingerprint.

In the above structured fingerprint verification method, since thefingerprint can be identified by comparing and verifying the storedcharacteristic information of a partial image and the characteristicinformation of the input partial image, the characteristic informationof the whole fingerprint is not necessary to be stored.

According to the fingerprint verification method of the presentinvention, at the characteristic information extracting step a frequencyanalysis computing process may be executed to extract frequency spectruminformation of the partial image of the fingerprint as thecharacteristic information.

In the above structured fingerprint verification method, thecharacteristics (minutia) are not extracted from the fingerprint.Information of the ridge is processed by the frequency analysiscomputing process to obtain the characteristic information. Therefore, apreprocessing time of the image can become short and the process can beexecuted fast. Moreover, there is no difference in difficulty ofextracting of the characteristics caused by a condition of a finger whenan image is inputted. Therefore, the process time can be stable.

According to the fingerprint verification method of the presentinvention, at the characteristic information extracting step, one of alinear predictive coding (LPC) computing process, a group delay spectrum(GDS) computing process and a fast Fourier transform (FFT) computingprocess may be used as the frequency analysis computing process.

In the above structured fingerprint verification method, thecharacteristic information can be extracted easily and fast to executethe fingerprint verification process by using the known frequencyanalysis computing process such as voice analysis.

According to the fingerprint verification method of the presentinvention, at the fingerprint inputting step, a line image of more thanor equal to one image line may be input as a partial image of afingerprint and at the image processing step an overlapped image linemay be detected from the two partial images of a fingerprint that arecontinuously input at the fingerprint inputting step and the overlappedimage line is removed from one of the two partial images of thefingerprint.

In the above structured fingerprint verification method, since every twoinputted partial images are processed and reconfigured, the memoryamount for storing the input partial images can be minimum. Further,since the input operation and the image process can be executed at thesame time, the operation can be executed fast.

According to the fingerprint verification method of the presentinvention, at the image processing step, an image reduction process maybe executed in at least one of a raster direction and a line directionof the partial image of the fingerprint where the overlapped portion isremoved.

In the above structured fingerprint verification method, for examplewhen the image reduction process is executed in a raster direction incase that the LPC calculation process is used for extracting thecharacteristic information, the dimension necessary for the calculationis decreased. Therefore, the memory amount for storing thecharacteristic information can be decreased. When the image reductionprocess is executed in a line direction, the number of times forcalculating the characteristic information is decreased. Therefore, thememory amount for storing the characteristic information can bedecreased.

According to the fingerprint verification method of the presentinvention, at the identifying step, the DP method (dynamic programmingmethod) may be used.

In the above structured fingerprint verification method, even if thedetection accuracy of the movement amount is low and the whole length ofthe fingerprint is different between the characteristic information ofthe registration time and the verification time, the difference betweenthe length of the fingerprints that are to be verified is absorbed andthe verification of the fingerprints can be executed.

A fingerprint verification program of the present invention forexecuting verification of a fingerprint based on an input image of afingerprint comprises a characteristic information extracting step ofcomputing and extracting a characteristic information from a partialimage of a fingerprint and an identifying step of executing thecharacteristic information extracting step with respect to more than orequal to one partial image of a fingerprint to extract a partialcharacteristic information of the fingerprint and identifying thefingerprint on the basis of the partial characteristic information.

In the above structured fingerprint verification program, since thecharacteristic information that is extracted from the partial image isused for identifying the fingerprint, it is not necessary to store awhole image of the fingerprint. Therefore, a large amount of memory forstoring the image of whole fingerprint is not necessary. Further, theimage of whole fingerprint may not be electronically copied. Since thepartial image is defined in small, the calculation amount for obtainingthe characteristic information can be reduced. If the characteristicinformation extracting process is executed separately from theidentifying process, the processes can be executed simultaneously andthe whole processes can be executed fast.

The fingerprint verification program of the present invention may have afingerprint inputting step of inputting a partial image of thefingerprint and image processing step of comparing a plurality ofpartial images of fingerprints inputted at the fingerprint inputtingstep and removing an overlapped portion. At the characteristicinformation extracting step the characteristic information may beextracted from the partial image of the fingerprint where the overlappedportion is removed at the image processing step.

In the above structured fingerprint verification program, a plurality ofpartial images that are input one after another are combined and theoverlapped portions are removed to be reconfigured. Therefore, it can beprevented that the characteristic information is extracted repeatedlyfrom the overlapped portion. Load for extracting the characteristicinformation can be reduced.

The fingerprint verification program of the present invention mayfurther have a storing step of storing a characteristic information ofat least one, and at the identifying step the at least onecharacteristic information stored at the storing step is compared andverified with at least one characteristic information that is extractedat the characteristic information extracting step to identify thefingerprint.

In the above structured fingerprint verification program, since thefingerprint can be identified by comparing and verifying the storedcharacteristic information of the partial image and the characteristicinformation of the input partial image, the characteristic informationof the whole fingerprint is not necessary to be stored.

According to the fingerprint verification program of the presentinvention, at the characteristic information extracting step a frequencyanalysis computing process is executed to extract frequency spectruminformation of the partial image of the fingerprint as thecharacteristic information.

In the above structured fingerprint verification program, thecharacteristics (minutia) are not extracted from the fingerprint.Information of the ridge is processed by the frequency analysiscomputing process to obtain the characteristic information. Therefore, apreprocessing time of the image can be short and the process can beexecuted fast. Moreover, there is no difference in difficulty ofextracting of the characteristics caused by a condition of a finger whenan image is inputted. Therefore, the process time can be stable.

According to the fingerprint verification program of the presentinvention, at the characteristic information extracting step, one of alinear predictive coding (LPC) computing process, a group delay spectrum(GDS) computing process and a fast Fourier transform (FFT) computingprocess may be used as the frequency analysis computing process.

In the above structured fingerprint verification program, thecharacteristic information can be extracted easily and fast to executethe fingerprint verification process by using the known frequencyanalysis computing process such as voice analysis.

According to the fingerprint verification program of the presentinvention, at the fingerprint inputting step, a line image of more thanor equal to one image line is input as a partial image of a fingerprintand at the image processing step an overlapped image line is detectedfrom the two partial images of a fingerprint that are continuously inputat the fingerprint inputting step and the overlapped image line isremoved from one of the partial images of the fingerprint.

In the above structured fingerprint verification program, since everytwo inputted partial images are processed and reconfigured, the memoryamount for storing the input partial images can be minimum. Further,since the input operation and the image process can be executed at thesame time, the operation can be executed fast.

According to the fingerprint verification program of the presentinvention, at the image processing step, an image reduction process maybe executed in at least one of a raster direction and a line directionof the partial image of the fingerprint where the overlapped portion isremoved.

In the above structured fingerprint verification program, for examplewhen the image reduction process is executed in a raster direction incase that the LPC calculation process is used for extracting thecharacteristic information, the dimension necessary for the calculationis decreased. Therefore, the memory amount for storing thecharacteristic information can be decreased. When the image reductionprocess is executed in a line direction, the number of times forcalculating the characteristic information is decreased. Therefore, thememory amount for storing the characteristic information can bedecreased.

According to the fingerprint verification program of the presentinvention, at the identifying step, the DP verification method (dynamicprogramming method) is used.

In the above structured fingerprint verification program, even if thedetection accuracy of the movement amount is low and the whole length ofthe fingerprint is different between the characteristic information ofthe registration time and the verification time, the difference betweenthe length of the fingerprints that are to be verified is absorbed andthe verification of the fingerprints can be executed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an outward appearance view of an electronic lock of oneembodiment,

FIG. 2 is a block diagram showing an electric structure of theelectronic lock of the embodiment,

FIG. 3 is a block diagram showing an electric structure of a fingerprintverification apparatus.

FIG. 4 is a diagrammatic view showing a storing area of a RAM 2,

FIG. 5 is a diagrammatic view showing a storing area of an EEP-ROM 4,

FIG. 6 is an example view of an input partial image,

FIG. 7 is an example view of an image that is obtained by areconfiguration process section 106,

FIG. 8 is an example view showing nine continuous partial images outputfrom the reconfiguration process section 106 that are aligned with eachother.

FIG. 9 is a flowchart showing a process flow of the electronic lock,

FIG. 10 is a flowchart showing details of a fingerprint registrationprocess,

FIG. 11 is a flowchart showing details of a fingerprint erasing process.

FIG. 12 is a flowchart showing details of a fingerprint input detectionprocess,

FIG. 13 is a flowchart showing details of a characteristics extractingprocess.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, one embodiment of the present invention that is applied toan electronic lock where a fingerprint verification apparatus is mountedwill be explained with reference to the drawings. As shown in FIG. 1,the electronic lock 100 has a fingerprint input device 7, switches 8 (afingerprint registration switch 8 a and a fingerprint erasing switch 8b) and a liquid crystal display 10. The electronic lock 100 is mountedto a door and the electronic lock 100 is locked by a plunger 9 a that ismoved by an electromagnetic solenoid 9 (referring to FIG. 2). As shownin FIG. 2, the electronic lock 100 of the embodiment is structured by anelectronic circuit including a CPU 1 and has a RAM 2, a ROM 3, anEEP-ROM 4, the fingerprint input device 7, the switches 8, aninput/output (I/O) port 5 for connecting the electromagnetic solenoid 9and the CPU 1, a liquid crystal display controller (LCDC) 6 forcontrolling the liquid crystal display 10 and an electric power sourcedevice such as a battery (not shown).

As shown in FIG. 4, the RAM 2 includes a partial image buffer memory 20for storing a slice image of a fingerprint input by the fingerprintinput device 7, an input characteristic information memory 21 forstoring a characteristic information of the input fingerprints, a jointjudgment storing memory 22 for storing computing result for judging thejoint portions and a work area 23 for temporary storing various data. Afinger print verification program and various programs are stored in theROM 3 and the electronic lock 100 is controlled when the CPU 1 executesa corresponding program.

As shown in FIG. 5, the EEP-ROM 4 has a registered characteristicinformation memory 40 for storing a characteristic information of aregistered fingerprint. Since the EEP-ROM 4 is a non-volatile memory,the stored data can be maintained even when the supply of the electricpower is stopped. For the EEP-ROM 4, a non-volatile memory such as aflash memory or the like can be used instead of a normal EEP-ROM.

As shown in FIG. 3, the fingerprint verification apparatus mounted inthe electronic lock 100 includes the fingerprint input device 7; animage process section 102; a fingerprint characteristic informationextracting section 110; a verification process section 114; a judgmentsection 115; a judgment result output section 116; a partial imagebuffer memory 20, an input characteristic information memory 21, and ajoint judgment storing memory 22 provided in the RAM 2; and a registeredcharacteristic information memory 40 of the EEP-ROM 4.

The fingerprint input device 7 includes a sensor 7 a and an A/Dconverter (not shown) and outputs an input partial image representingtemperature change of a finger that moves on the sensor 7 a and theinput partial image is stored in the partial image buffer memory 20 ofthe RAM 2. In the embodiment, the input partial image is formed in alinear shape of 280 pixels in a horizontal direction and 8 pixels in avertical direction and the input partial image is output more than orequal to 200 times a second. One example of the input partial image isshown in FIG. 6.

The image process section 102 executes a previous operation so that acharacteristic information can be extracted from the input partialimage. The image process section 102 includes a start judgment section103, a movement value detection section 104, an overlapping processsection 105, a reconfiguration process section 106, a joint judgmentpreprocessing section 107, a joint judgment storing memory 22 and animage reduction process section 109.

The start judgment section 103 extracts a center portion (64 pixels in ahorizontal direction and 4 pixels in a vertical direction in theembodiment) from continuous two input partial images that are obtainedby the fingerprint input device 7 and computes difference of a pictureelement value at a same portion as an absolute value. When the number oftimes that the difference value exceeds a threshold reaches more than orequal to a predetermined number of times, it is judged that a fingermoves on the fingerprint input device 7 and data is started to be storedin the joint judgment storing memory 22 and the input characteristicinformation memory 21. When the number of times that the differencevalue becomes lower than the threshold reaches more than or equal to apredetermined number of times, it is judged that the finger is apartfrom the input device and the data is stopped to be stored in eachmemory. Afterwards, the verification is operated with the verificationprocess section 114.

The movement detection portion 104 extracts a center portion (64 pixelsin a horizontal direction and 8 pixels in a vertical direction in theembodiment) of one of the continuous two input partial images that areinput by the fingerprint input device 7. Next, the movement valuedetection portion 104 extracts a portion of a same size as the centerportion from the another input partial image. The portion to beextracted is obtained by shifting with an assumed movement value.Difference between the picture element values of the same portion in theextracted partial images is computed as the absolute value and theobtained value is considered as image difference. This process isrepeatedly executed for the assumed movement value. When the imagedifference becomes minimum, the movement value at this time isconsidered as output as a detection result of the movement value of thefinger that moves on the sensor 7 a.

The overlapping process section 105 adds the value in the memory and thevalue of the input image to store in the same portion with respect tothe position of the buffer memory from by shifting the input partialimage that is obtained by the fingerprint input device 7 by the movementvalue obtained by the movement value detection portion 104. Thus, theimages are overlapped with each other. At this time, the number ofoverlapping times is also stored in the buffer memory.

The reconfiguration process section 106 reconfigures the image obtainedby the fingerprint input device 7 based on the movement value obtainedby the movement value detection section 104 to output a partial image(280 pixels in a horizontal direction and 1 pixel in a verticaldirection in this embodiment) as an unit. FIG. 7 shows an example whenthe whole image is obtained by the reconfiguration process section 106.FIG. 8 shows an example when nine continuous partial images that areoutput from the reconfiguration process section 106 are aligned witheach other.

The joint judgment preprocessing section 107 executes a part ofcomputing necessary for judging the joint portion of a finger that moveson the sensor 7 a and outputs the computing result to store it in thejoint judgment storing memory 22. First, sobel transform is executed tothe input image to emphasize the characteristics of the fingerprint.Next, gauss transform is executed to decrease noise picture elements.Next, one line (256 pixels in a horizontal direction and 1 pixel in avertical direction in this embodiment) is extracted and the number ofpicture elements whose picture element value exceeds the threshold ismeasured. This is a process result of the line. The value isproportional to the area where the finger contacts on the sensor 7 a. Itis judged that a part of the small value is a joint and only a portionhaving effective information is utilized as data for verification. Thejudgment section 115 judges the position of the joint using the valuestored in the joint judgment storing memory 22 after the finger is apartfrom the sensor 7 a and determines an end point of the verification.

The image reduction process section 109 reduces the image output fromthe reconfiguration process section 106 into an image of ½ in ahorizontal direction and ⅓ in a vertical direction. By the reduction ina horizontal direction, the dimension necessary for extracting thecharacteristics by LPC analysis can be decreased. By the reduction in avertical direction, the volume of the input characteristic informationmemory 21 can be reduced without spoiling the verification result.

The fingerprint characteristic extracting section 110 extractscharacteristics from the input one line after reduction (128 pixels in ahorizontal direction and 1 pixel in a vertical direction in thisembodiment) and outputs the characteristic data. In this embodiment, theLPC analysis is executed with the picture element value of the line assignal change.

The input characteristic information memory 21 continuously storescharacteristic data output from the fingerprint characteristicinformation extracting section 110. When the fingerprint verificationprocess is executed, the input characteristic information memory 21outputs the characteristic data according to the request from theverification process section 114. The registered characteristicinformation memory 40 of the EEP-ROM 4 stores and maintains the contentsof the input characteristic memory 21 when directed to register afingerprint. When the fingerprint verification process is executed, theregistered characteristic information memory 40 outputs thecharacteristic data according to the request from the verificationprocess section 114.

The verification process section 114 executes DP method to verify thecharacteristic data stored in the input characteristic informationmemory 21 with the characteristic data stored in the registeredcharacteristic information memory 40 of the EEP-ROM 4. The minimumdistance is represented as distance between the characteristics andoutputs as a degree of similarity. The judgment section 115 compares thedegree of similarity output from the verification process section 114with the previously set threshold to execute judgment. The result isoutput to the judgment result output section 116. The judgment resultoutput section 116 inputs the judgment result output from the judgmentsection 115 and outputs the judgment result outside of the apparatus.

Next, an operation of the electronic lock 100 of this embodiment will beexplained with reference to the flowcharts of FIGS. 9 to 13.Hereinafter, each step of the flowcharts is described as S. In theelectronic lock 100 of this embodiment, a fingerprint is registered whenthe fingerprint registration switch 8 a is pressed and a finger isplaced on the fingerprint input device 7 and moved in its longitudinaldirection so as to be slid. Then the plunger 9 a comes out to lock theelectronic lock 100. When the finger is placed on the fingerprint inputdevice 7 without pressing the fingerprint registration switch 8 a andthe finger is moved in its longitudinal direction so as to be slid, thefingerprint verification is executed. If the input fingerprint isidentified with a registered fingerprint, the plunger 9 a comes back andthe electronic lock 100 is unlocked. A fingerprint is input when thefingerprint erase switch 8 b is pressed and the finger is placed on thefingerprint input device 7 and moved in its longitudinal direction so asto be slid. In this case, after confirmation is displayed on the liquidcrystal display 10, the registered identified fingerprint is erased ifthe fingerprint erase switch 8 b is pressed again.

FIG. 9 is a flowchart showing a whole main control process of theelectronic lock 100. First, when an electric power is turned on, theelectronic lock 100 is reset and memories and the like in the RAM 2 areinitialized (S40). It is detected whether any one of switches 8 ispressed (S41) and if the fingerprint registration switch 8 a is pressed(S42:YES), the fingerprint registration process is executed (S43). Ifthe fingerprint erase switch 8 b is pressed (S42:NO, S44:YES), thefingerprint erase process is executed (S45). Details of the fingerprintregistration process and the fingerprint erase process will be explainedlater. If any one of the switches is not pressed (S44:NO), it isdetected whether a fingerprint is input (S46). Details of thefingerprint input detection process will be explained later. If anyfingerprint is not input (S47:NO), the process returns to S41 to detectwhether any switch is input. If a fingerprint is input (S47:YES) and itis judged that the input fingerprint is identified with a registeredfingerprint (S48:YES), the plunger 9 a is pulled back to unlock theelectronic lock 100 (S49).

FIG. 10 is a flowchart showing details of the fingerprint registrationprocess executed at S43 in FIG. 9. When a finger is placed on thefingerprint input device 7 and moved in its longitudinal direction so asto be slid, a partial image shown in FIG. 6 is input from the sensor 7 a(S50). Since the sensor 7 a detects image input every predetermined time(equal to or more than 200 times a second in this embodiment), one or aplurality of partial images are input depending on the speed that thefinger is moved. The input partial image is stored in the partial imagebuffer memory 20 of the RAM 2 (S51).

If only one partial image input is detected and only one partial imageis stored in the partial image buffer memory 20, an error is caused andthe process is terminated to return to the main routine (S52:NO). If aplurality of partial images are stored in the buffer memory 20(S52:YES), the movement value detection section 104 detects the movementvalue. The reconfiguration process section 106 corrects and reconfiguresa portion where the partial images are overlapped based on the detectedmovement value (S53).

Reconfiguration is executed as follows. The image corresponding to themovement value that is not overlapped with the partial image that isinput later (present frame) is separated from the partial image that isinput before (old frame) and stored in the work area 23 of the RAM 2.Next, the overlapping process section overlaps the images at theoverlapped portion of the old frame and the present frame and theoverlapped images are stored in the work area 23 of the RAM 2. A portionwhere the present frame and the old frame are not overlapped is storedin the work area 23 of the RAM 2. The fingerprint characteristicextracting section 110 extracts the characteristics from thereconfigured partial image (S54) and the characteristics are stored inthe input characteristic information memory 21 and also in theregistration characteristic information memory 40 of the EEP-ROM 44(S55). Details of the characteristic information extracting process willbe explained later.

FIG. 11 is a flowchart showing details of the fingerprint erase processthat is executed at S45 of FIG. 9. When a finger is placed on thefingerprint input device 7 and moved in its longitudinal direction so asto be slid, the partial image shown in FIG. 6 is input from the sensor(S60). Since the sensor detects image input every predetermined time(equal to or more than 200 times a second in this embodiment), one or aplurality of partial images are input depending on the speed that thefinger is moved. The input partial image is stored in the partial imagebuffer memory 20 (S61).

If only one partial image input is detected and only one partial imageis stored in the partial image buffer memory 20, an error is caused andthe process is terminated to return to the main routine (S62:NO). If aplurality of partial images are stored in the buffer memory 20(S62:YES), the movement value detection section 104 detects the movementvalue. The reconfiguration process section 106 corrects and reconfiguresa portion where the partial images are overlapped based on the detectedmovement value (S63).

Reconfiguration is executed as follows. The image corresponding to themovement value that is not overlapped with the partial image that isinput later (present frame) is separated from the partial image that isinput before (old frame) and stored in the work area 23 of the RAM 2.Next, the overlapping process section overlaps the images at theoverlapped portion of the old frame and the present frame and theoverlapped images are stored in the work area 23 of the RAM 2.

The fingerprint characteristic extracting section 110 extracts thecharacteristics from the reconfigured partial image (S64) and thecharacteristics are stored in the input characteristic informationmemory 21 (S65). Details of the characteristic information extractingprocess will be explained later.

It is judged whether the characteristic information stored in the inputcharacteristic information memory 21 is more than or equal to apredetermined length (for example 500 lines) (S66). If thecharacteristic information stored in the input characteristicinformation memory 21 is smaller than the predetermined amount, thecomparison and the verification are difficult and an error is caused.The process is terminated and returns to the main routine (S66:NO). Ifthe characteristic information stored in the characteristic informationmemory 21 is more than or equal to the predetermined amount (S66:YES),DP comparison (dynamic programming method) is executed by theverification process section 114 between the characteristic informationstored in the input characteristic information memory 21 and thecharacteristic information stored in the registered characteristicinformation memory 40 of the EEP-ROM 4 (S67).

The DP comparison (dynamic programming method) is called as DP matchingor rubber matching. The DP comparison is widely known. In the DPcomparison, matching can be executed smoothly for the varied data. TheDP comparison is an algorism where in the two lines of reference dataand test data are put on an x-y plane to select a time sequence so thatthe accumulated distance becomes smallest with taking distancedifference of the real data into consideration.

In this embodiment, LPC cepstrum (that will be explained later) obtainedin the characteristic information extracting process (that will beexplained later) of S64 is considered as spectrum data for everyfingerprint line. The LPC cepstrum obtained from the input fingerprintimage is aligned with the vertical direction of the fingerprint imageand the aligned data is considered as test data. The LPC cepstrum storedin the registered characteristic information memory 40 of the EEP-ROM 4is aligned with the vertical direction of the fingerprint image isconsidered as reference data. The degree of matching is obtained betweenthe test data and the reference data.

The input speed change and the change degree are different between thereference data and the test data. Taking the difference intoconsideration, the correspondence in the vertical direction is searchedby the DP comparison so that the reference data and the test data areclosest at the end. At the closest vertical correspondence, the matchingdegree is output as a distance value. If the distance value becomessmaller, the difference between the LPC cepstrum of the reference dataand of the test data is small. If the distance value becomes larger, thedifference between the LPC cepstrum of the reference data and of thetest data is large.

The judgment section 115 compares the distance value obtained by the DPcomparison with a threshold that is previously set. It is judged thatthe fingerprint is identified if the distance value is smaller than thethreshold and it is judged that the fingerprint is not identified if thedistance value is larger than the threshold (S68). If not identified,the registered fingerprint is not erased from the registeredcharacteristic information memory 40 of the EEP-ROM 4 and the process isterminated and returns to the main routine (S69:NO). If identified, thecharacteristic information of the registered fingerprint that isidentified is erased from the registered characteristic informationmemory 40 of the EEP-ROM 4 (S70).

FIG. 12 is a flowchart showing details of the fingerprint inputdetection process that is executed at S46 in FIG. 9. When a finger isplaced on the fingerprint input device 7 and the finger is moved in itslongitudinal direction, a partial image shown in FIG. 6 is input fromthe sensor (S80). The sensor detects the input for every predeterminedtime (more than or equal to 200 times a second in this embodiment). Oneor a plurality of partial images are input depending on the speed atwhich the finger is moved.

The input partial image is stored in the partial image buffer memory 20(S81). If the input of only one partial image is detected and only onepartial image is stored in the partial image buffer memory 20, an erroris caused and the process is terminated and returns to the main routine(S82:NO). If a plurality of partial images are stored in the partialimage buffer memory 20 (S82:YES), the movement value is detected by themovement value detection section 104. The overlapped portion of thepartial image is corrected and reconfigured by the reconfigurationprocess section 106 based on the detected movement value (S83).

Reconfiguration is executed as follows. The image corresponding to themovement value that is not overlapped with the partial image that isinput later (present frame) is separated from the partial image that isinput before (old frame) and stored in the work area 23 of the RAM 2.Next, the overlapping process section overlaps the images at theoverlapped portion of the old frame and the present frame and theoverlapped images are stored in the work area 23 of the RAM 2. Thefingerprint characteristic extracting section 110 extracts thecharacteristics from the reconfigured partial image (S84) and thecharacteristics are stored in the input characteristic informationmemory 21 (S85). Details of the characteristic information extractingprocess will be explained later.

It is judged whether the characteristic information stored in the inputcharacteristic information memory 21 is more than or equal to apredetermined length (for example 500 lines) (S86). If thecharacteristic information stored in the input characteristicinformation memory 21 is smaller than the predetermined amount, thecomparison and the verification are difficult and an error is caused.The process is terminated and returns to the main routine (S86:NO). Ifthe characteristic information stored in the characteristic informationmemory 21 is more than or equal to the predetermined amount (S86:YES),DP comparison (dynamic programming method) is executed by theverification process section 114 between the characteristic informationstored in the input characteristic information memory 21 and thecharacteristic information stored in the registered characteristicinformation memory 40 of the EEP-ROM 4 (S87).

The judgment section 115 compares the distance value obtained by the DPcomparison with a threshold that is previously set. It is judged thatthe fingerprint is identified if the distance value is smaller than thethreshold and it is judged that the fingerprint is not identified if thedistance value is larger than the threshold (S88). The process isterminated and returns to the main routine.

FIG. 13 is a flowchart showing details of the characteristic informationextracting process that is executed at S54 of FIG. 10, S64 of FIG. 11and S84 of FIG. 12. In this embodiment, the characteristics (minutia)are not extracted from the fingerprint. Information of the ridge isanalyzed to obtain the characteristic information.

A line is extracted from the fingerprint image in alignment with itshorizontal direction and the position of the fingerprint is representedin the horizontal direction and the density degree of the fingerprint isrepresented in the vertical direction to obtain a wave form signal. Whenthe known analysis that is generally executed in the voice data processis executed to the waveform signal, power spectrum is obtained.

Each line of the reconfigured input partial image is considered as oneframe and the extracting process is executed for each frame. Aspreprocessing, hamming windowing is executed (S90) to correct the endportions of the extracted frame. The auto correlation is obtained fromthe frame data that the correction process of the humming windowing isexecuted (S91).

The LPC coefficient is computed by the linear predictive coding (LPC)based on the obtained autocorrelation (S92). The linear predictivecoding is known technology that is used for the voice compression suchas in a portable phone. By the linear predictive coding, the voices suchas vowels can be predicted with all pole transfer function and the peakfrequency can be predicted from the spectrum.

The LPC coefficient obtained at S92 is computed with a linearcombination operation to obtain the LPC cepstrum (S93). In thisembodiment, the LPC cepstrum obtained during the characteristicinformation extracting process is stored in the input characteristicinformation memory 21 of the RAM 2 as the characteristic information(S55, S65, S85).

In this embodiment, the linear predictive coding (LPC) is used for thefrequency analysis computing process for extracting the characteristicinformation and the LPC cepstrum is extracted as the characteristicinformation. The frequency analysis computing process for extracting thecharacteristic information is not limited to the LPC. For example, theknown fast Fourier transform may be used for the frequency analysiscomputing process. The fast Fourier transform is an algorism thatexecutes with high speed the computing process for computing thefrequency component (spectrum) of the discrete Fourier transform that isa digital signal. The weighted LPC coefficient obtained at S92 istransformed with the fast Fourier transform to obtain a power spectrumand the obtained power spectrum is used as the characteristicinformation.

The known group delay spectrum may be used for the frequency analysiscomputing process used for extracting the characteristic information.The group delay spectrum is defined as the frequency differential of thephase spectrum in the power transfer function.

The number of elements of the arrangement is the obtained numbersubtracted one from the number of elements of the phase spectrum. Theweighted LPC coefficient is transformed with the fast Fourier transformto obtain the power spectrum. The phase differential of the obtainedpower spectrum is obtained to obtain the group delay spectrum as thecharacteristic information.

As explained above, in the fingerprint verification apparatus of theembodiment, the characteristics (minutia) are not extracted from thefingerprint. Information of the ridge is considered as a waveform signaland processed by the frequency analysis computing process to obtain thecharacteristic information.

Therefore, the process time for extracting the characteristicinformation can be stable in regardless of the condition of thefingerprint. The characteristic information can be extracted form thepartial image without storing the whole image of the fingerprint.

Therefore, compared to the conventional fingerprint verification methodwherein the characteristic data is extracted from the whole image of thefingerprint, the verification can be executed with a small amount ofmemory and the fingerprint verification apparatus can be light and theprocess can be executed with high speed. Since it is not necessary tostore the whole image of the fingerprint, it can be prevented to cause aproblem of security such as electronic copy of a fingerprint.

Since the characteristic information is extracted from the partialimage, the overlapping of the extracting process may be caused by theoverlapping of the input images. However, the overlapping of theextracting process is prevented by the reconfiguration of the images.Since the characteristic information is extracted from the partialimage, the input characteristic information may be different from theregistered characteristic information for every input of thefingerprint, however, the difference is absorbed by executing the DPcomparison (DP matching) and verification is executed.

The present invention may be modified in many other specific forms. Forexample, in the above embodiment, the present invention is applied to anelectronic lock, however, the present invention may be applied to othervarious apparatuses for verifying fingerprints. In the above embodiment,the fingerprint verification program is stored in the ROM 3, however, itis not limited thereto. The fingerprint verification program may bestored in the storing medium that can be read by a computer such as afloppy disc or a CD-ROM, or may be sent via a network such as internet.

INDUSTRIAL APPLICABILITY

As described above, the fingerprint verification apparatus, thefingerprint verification method and the fingerprint verification programof the present invention are preferable to be used for a variousapparatus for verifying fingerprints. Particularly, the presentinvention is preferable to be used in an electronic lock that isunlocked by the fingerprint verification, an electronic apparatus thatstarts to be operated by the fingerprint verification or an informationterminal such as portable phone that verify fingerprints.

1. A fingerprint verification apparatus for verifying a fingerprintbased on an input image of a fingerprint comprising: fingerprint inputmeans for inputting a partial image of the fingerprint; image processmeans for comparing a plurality of partial images of fingerprintsinputted by the fingerprint input means and reconfiguring individualpartial images to remove an overlapped portion; characteristicinformation extracting means for computing and extracting characteristicinformation from a reconfigured partial image of the fingerprint, whereany overlapped portion is removed by the image process means; andidentifying means for identifying the fingerprint on the basis of thecharacteristic information of the partial image of the fingerprintextracted by the characteristic information extracting means, wherein atleast two of the inputting the partial image of the fingerprint,removing the overlapped portion, and extracting the characteristicinformation are performed simultaneously.
 2. The fingerprintverification apparatus according to claim 1, further comprising storingmeans for storing a characteristic information of at least one partialimage, wherein the identifying means compares and verifies at least onecharacteristic information stored by the storing means with at least onecharacteristic information that is extracted by the characteristicinformation extracting means to identify the fingerprint.
 3. Thefingerprint verification apparatus according to claim 1, wherein thecharacteristic information extracting means executes a frequencyanalysis computing process to extract frequency spectrum information ofthe partial image of the fingerprint as the characteristic information.4. The fingerprint verification apparatus according to claim 3, whereinthe characteristic information extracting means uses one of a linearpredictive coding (LPC) computing process, a group delay spectrum (GDS)computing process and a fast Fourier transform (FFT) computing processas the frequency analysis computing process.
 5. The fingerprintverification apparatus according to claim 1, wherein the fingerprintinput means inputs a line image of one or more image lines as a partialimage of a fingerprint and the image process means detects an overlappedimage line in the two partial images of fingerprints that arecontinuously input by the fingerprint input means and removes theoverlapped image line from one of the two partial images offingerprints.
 6. The fingerprint verification apparatus according toclaim 1, wherein the image process means executes an image sizecontraction process in at least one of a raster direction and a linedirection of the partial image of the fingerprint where the overlappedportion is removed.
 7. The fingerprint verification apparatus accordingto claim 3, wherein the identifying means uses a DP method (dynamicprogramming method).
 8. A fingerprint verification method for verifyinga fingerprint based on an input image of a fingerprint comprising: afingerprint inputting step of inputting a partial image of thefingerprint; an image processing step of comparing a plurality ofpartial images of fingerprints inputted at the fingerprint inputtingstep and reconfiguring individual partial images to remove an overlappedportion; a characteristic information extracting step of computing andextracting a characteristic information from a reconfigured partialimage of the fingerprint, where any overlapped portion is removed at theimage processing step; and an identifying step of identifying thefingerprint on the basis of the characteristic information of thepartial image of the fingerprint extracted at the characteristicinformation extracting step, wherein at least two of the fingerprintinputting step, the image processing step, and the characteristicinformation extracting step are performed simultaneously.
 9. Thefingerprint verification method according to claim 8, further comprisinga storing step of storing a characteristic information of at least onepartial image, wherein at the identifying step at least onecharacteristic information stored at the storing step is compared andverified with at least one characteristic information that is extractedat the characteristic information extracting step to identify thefingerprint.
 10. The fingerprint verification method according to claim8, wherein at the characteristic information extracting step a frequencyanalysis computing process is executed to extract frequency spectruminformation of the partial image of the fingerprint as thecharacteristic information.
 11. The fingerprint verification methodaccording to claim 10, wherein at the characteristic informationextracting step one of linear predictive coding (LPC) computing process,a group delay spectrum (GDS) computing process and a fast Fouriertransform (FFT) computing process is used as the frequency analysiscomputing process.
 12. The fingerprint verification method according toclaim 8, wherein at the fingerprint inputting step a line image of oneor more image lines is input as a partial image of a fingerprint and atthe image processing step an overlapped image line is detected in thetwo partial images of fingerprints that are continuously input at thefingerprint inputting step and the overlapped image line is removed fromone of the two partial images of fingerprints.
 13. The fingerprintverification method according to claim 8, wherein at the imageprocessing step an image size contraction process is executed in atleast one of a raster direction and a line direction of the partialimage of the fingerprint where the overlapped portion is removed. 14.The fingerprint verification method according to claim 10, wherein atthe identifying step a DP method (dynamic programming method) is used.15. A computer-readable medium that stores a fingerprint verificationprogram for causing a computer to execute verification of a fingerprintbased on an input image of a fingerprint comprising: a fingerprintinputting step of inputting a partial image of the fingerprint; an imageprocessing step of comparing a plurality of partial images offingerprints inputted at the fingerprint inputting step andreconfiguring individual partial images to remove an overlapped portion;a characteristic information extracting step of computing and extractinga characteristic information from a reconfigured partial image of thefingerprint, where any overlapped portion is removed at the imageprocessing step; and an identifying step of identifying the fingerprinton the basis of the characteristic information of the partial image ofthe fingerprint extracted at the characteristic information extractingstep, wherein at least two of the fingerprint inputting step, the imageprocessing step, and the characteristic information extracting step areperformed simultaneously.
 16. The computer-readable medium according toclaim 15, further comprising a storing step of storing a characteristicinformation of at least one partial image, wherein at the identifyingstep at least one characteristic information stored at the storing stepis compared and verified with at least one characteristic informationthat is extracted at the characteristic information extracting step toidentify the fingerprint.
 17. The computer-readable medium according toclaim 15, wherein at the characteristic information extracting step afrequency analysis computing process is executed to extract frequencyspectrum information of the partial image of the fingerprint as thecharacteristic information.
 18. The computer-readable medium accordingto claim 17, wherein at the characteristic information extracting stepone of a linear predictive coding (LPC) computing process, a group delayspectrum (GDS) computing process and a fast Fourier transform (FFT)computing process is used as the frequency analysis computing process.19. The computer-readable medium according to claim 15, wherein at thefingerprint inputting step a line image of one or more image lines isinput as a partial image of a fingerprint and at the image processingstep an overlapped image line is detected in the two partial images offingerprints that are continuously input at the fingerprint inputtingstep and the overlapped image line is removed from one of the twopartial images of fingerprints.
 20. The computer-readable mediumaccording to claim 15, wherein at the image processing step an imagesize contraction process is executed in at least one of a rasterdirection and a line direction of the partial image of the fingerprintwhere the overlapped portion is removed.
 21. The computer-readablemedium according to claim 17, wherein at the identifying step a DPmethod (dynamic programming method) is used.
 22. The fingerprintverification apparatus according to claim 1, wherein the characteristicinformation extracting means extracts the characteristic informationfrom an extracted line of a reconfigured partial image.
 23. Thefingerprint verification apparatus according to claim 1, wherein theinputting the partial image of the fingerprint and extracting thecharacteristic information are performed simultaneously.
 24. Thefingerprint verification method according to claim 8, wherein at thefingerprint inputting step and the characteristic information extractingstep are performed simultaneously.
 25. The computer-readable mediumaccording to claim 17, wherein the fingerprint inputting step and thecharacteristic information extracting step are performed simultaneously.